Subsea Control Modules (SCM's) are commonly used in the oil and gas industry. Most SCM's have a plate for attaching the SCM to a subsea tree, a sealed electronics chamber and a series of valves that can be used to control fluid and electrical lines that pass through the tree and into a well. The sealed electronics chamber is often referred to as a Subsea Electronics Module (SEM).
There are many different designs of SEM's but most comprise an opened ended canister and a cap that fits onto and closes the canister. The cap has an electrical connector with electrical connections that provide electrical communication between electrical components inside the canister and the outside.